Cement compositions comprising high aspect ratio materials and methods of use in subterranean formations

ABSTRACT

Cement compositions that include high aspect ratio materials, and methods for using such cement compositions in subterranean formations are provided herein. An example of a method is a method of cementing in a subterranean formation. An example of a composition is a cement composition for use in a subterranean formation.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.10/884,756, filed Jul. 2, 2004, entitled “Cement Compositions ComprisingHigh Aspect Ratio Materials And Methods Of Use In SubterraneanFormations,” by B. Raghava Reddy, et al., which is incorporated byreference herein for all purposes, from which priority is claimedpursuant to 35 U.S.C. § 120.

BACKGROUND OF THE INVENTION

The present invention relates to subterranean well cementing operations,and more particularly, to cement compositions comprising high aspectratio materials and methods for using such cement compositions insubterranean formations.

Hydraulic cement compositions commonly are utilized in subterraneanoperations, particularly subterranean well completion and remedialoperations. For example, hydraulic cement compositions are used inprimary cementing operations whereby pipe strings, such as casing andliners, are cemented in well bores. In performing primary cementing, ahydraulic cement composition is pumped into an annular space between thewalls of a well bore and the exterior surface of the pipe stringdisposed therein. The cement composition sets in the annular space,thereby forming therein an annular sheath of hardened, substantiallyimpermeable cement that supports and positions the pipe string in thewell bore and bonds the exterior surface of the pipe string to the wallsof the well bore. Hydraulic cement compositions also are used inremedial cementing operations, such as plugging highly permeable zonesor fractures in well bores, plugging cracks and holes in pipe strings,and the like.

Once set, the cement sheath may be subjected to a variety of shear,tensile, impact, flexural, and compressive stresses that may lead tofailure of the cement sheath, resulting in, inter alia, fractures,cracks, and/or debonding of the cement sheath from the pipe stringand/or the formation. This can lead to undesirable consequencesincluding, inter alia, lost production, environmental pollution,hazardous rig operations resulting from unexpected fluid flow from theformation caused by the loss of zonal isolation, and/or hazardousproduction operations. Cement failures may be particularly problematicin high temperature wells, where fluids injected into the wells orproduced from the wells by way of the well bore may cause thetemperature of any fluids trapped within the annulus to increase.Furthermore, high fluid pressures and/or temperatures inside the pipestring may cause additional problems during testing, perforation, fluidinjection, and/or fluid production. If the pressure and/or temperatureinside the pipe string increases, the pipe may expand and stress thesurrounding cement sheath. This may cause the cement sheath to crack, orthe bond between the outside surface of the pipe string and the cementsheath to fail, thereby breaking the hydraulic seal between the two.Furthermore, high temperature differentials created during production orinjection of high temperature fluids through the well bore may causefluids trapped in the cement sheath to thermally expand, causing highpressures within the sheath itself. Additionally, failure of the cementsheath also may be caused by, inter alia, forces exerted by shifts insubterranean formations surrounding the well bore, cement erosion, andrepeated impacts from the drill bit and the drill pipe.

SUMMARY OF THE INVENTION

The present invention relates to subterranean well cementing operations,and more particularly, to cement compositions comprising high aspectratio materials and methods for using such cement compositions insubterranean formations.

One example of a method of the present invention is a method ofcementing in a subterranean formation, comprising providing a cementcomposition comprising water, cement, and a high aspect ratio materialselected from glass fibers and non-fibrous minerals; introducing thecement composition into a subterranean formation; and allowing thecement composition to set therein.

Another example of a method of the present invention is a method ofcementing in a subterranean formation, comprising: providing a cementcomposition comprising water, cement, and glass fibers having a meanaspect ratio in the range of from about 1.25 to about 5,000; introducingthe cement composition into a subterranean formation; and allowing thecement composition to set therein.

Another example of a method of the present invention is a method ofcementing in a subterranean formation, comprising: providing a cementcomposition comprising water, cement, and a non-fibrous mineral having amean aspect ratio of at least about 50; introducing the cementcomposition into a subterranean formation; and allowing the cementcomposition to set therein.

The features and advantages of the present invention will be readilyapparent to those skilled in the art upon a reading of the descriptionof the preferred embodiments that follows.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention relates to subterranean well cementing operations,and more particularly, to cement compositions comprising high aspectratio materials and methods for using such cement compositions insubterranean formations.

Certain embodiments of the cement compositions of the present inventioncomprise cement, water, and a high aspect ratio material that comprisesnon-amorphous metallic fibers, alkali-resistant glass fibers,non-fibrous minerals, or a mixture thereof. As referred to herein, theterm “aspect ratio” will be understood to mean the ratio of a solidbody's length to its width.

Any cement suitable for use in subterranean cementing operations may beused in accordance with the present invention. In one embodiment, theimproved cement compositions of the present invention comprise ahydraulic cement. A variety of hydraulic cements are suitable for use,including those comprising calcium, aluminum, silicon, oxygen, and/orsulfur, which set and harden by reaction with water. Such hydrauliccements include, but are not limited to, Portland cements, pozzolaniccements, gypsum cements, soil cements, calcium phosphate cements, highalumina content cements, silica cements, high alkalinity cements, andmixtures thereof. In certain embodiments, the cement compositions of thepresent invention may comprise a Portland cement. In certainembodiments, the Portland cement may be chosen from those classified asClass A, C, G, and H cements according to API Specification forMaterials and Testing for Well Cements, API Specification 10, Fifth Ed.,Jul. 1, 1990. Another cement that may be useful in certain embodimentsof the present invention is commercially available under the trade name“THERMALOCK™” from Halliburton Energy Services, Inc., of Duncan, Okla.Other cements that may be suitable for use in accordance with thepresent invention include, inter alia, low-density cements. Suchlow-density cements may be, inter alia, foamed cements or cementscomprising another means to reduce their density, such as hollowmicrospheres, low-density elastic beads, fly ashes, blast furnace slag,or other density-reducing additives known in the art.

Generally, the water utilized in the cement compositions of the presentinvention may be fresh water, salt water (e.g., water containing one ormore salts dissolved therein), brine (e.g., saturated salt water), orseawater. This water may be from any source, provided that the waterdoes not contain an excess of compounds (e.g., dissolved organics) thatmay adversely affect other components in the cement composition. In someembodiments, the water may be present in the cement compositions of thepresent invention in an amount sufficient to form a pumpable slurry. Incertain embodiments, the water is present in the cement compositions ofthe present invention in an amount in the range of from about 30% toabout 180% by weight of cement (“bwoc”) therein. In certain embodiments,the water is present in the cement compositions of the present inventionin an amount in the range of from about 40% to about 50% bwoc therein.One of ordinary skill in the art, with the benefit of this disclosure,will recognize the appropriate amount of water for a chosen application.

The cement compositions of the present invention also comprise a highaspect ratio material that comprises non-amorphous (e.g., crystalline)metallic fibers, alkali-resistant glass fibers, non-fibrous minerals, ora mixture thereof. In certain embodiments, the non-amorphous metallicfibers may be obtained by cold drawing low-carbon steel wires (e.g.,steel wool). Suitable metallic fibers include, but are not limited to,chopped steel fibers, stainless steel fibers, brass fibers, bronzefibers, nickel fibers, and titanium fibers. In certain embodiments ofthe present invention, the non-amorphous metallic fibers are low-carbonchopped steel wool fibers. Examples of suitable metallic fibers include,inter alia, those that are commercially available from Global MaterialTechnologies, of Palatine, Ill., under the trade names “GMT-2136,”“GMT-180,” and “GMT-380.” In certain embodiments wherein steel fibersare used, the steel fibers may comprise carbon present in an amount inthe range of from about 0.06% to about 0.11% by weight. In certainembodiments of the present invention wherein the high aspect ratiomaterial comprises non-amorphous metallic fibers, the non-amorphousmetallic fibers generally have a mean diameter in the range of fromabout 0.025 millimeters to about 0.10 millimeters, and a mean length inthe range of from about 0.1 millimeter to about 10 millimeters. As willbe appreciated by one of ordinary skill in the art, with the benefit ofthis disclosure, the length and diameter of the non-amorphous metallicfibers may be adjusted to enhance properties such as their flexibilityand ease of dispersion in the cement compositions of the presentinvention. In certain embodiments of the present invention wherein thehigh aspect ratio material comprises non-amorphous metallic fibers, thenon-amorphous metallic fibers generally have an aspect ratio in therange of from about 1.25 to about 400. In certain embodiments, thenon-amorphous metallic fibers may have an aspect ratio in the range offrom about 15 to about 200, and in certain other embodiments, from about25 to about 100. In certain embodiments of the present invention whereinthe high aspect ratio material comprises non-amorphous metallic fibers,the metallic fibers may be present in the cement compositions of thepresent invention in an amount in the range of from about 0.5% to about10% bwoc. Due to their density, certain metallic fibers may exhibit apropensity to settle out of the cement compositions of the presentinvention. Therefore, certain embodiments of the cement compositions ofthe present invention that comprise non-amorphous metallic fibers alsomay comprise a settling-prevention additive, such as a viscosifier, thatmay eliminate, or at least reduce, settling. Suitablesettling-prevention additives include, inter alia,hydroxyethylcellulose, and xanthan gum. A suitable settling-preventionadditive is commercially available from Halliburton Energy Services,Inc., under the trade name “FWCA.” Where settling-prevention additivesare included in the cement composition, they should be present in thecement composition in an amount that facilitates a uniform densitythroughout the cement composition.

In certain embodiments, the non-amorphous metallic fibers may be coatedby, e.g., surfactants that may inhibit any reaction that may occurbetween the cement composition and the metallic fibers. Examples ofsuitable surfactants that may be used to coat the non-amorphous metallicfibers include, inter alia, hydrophobic organic materials such assorbitol mono-oleate, sorbitol tri-oleate, and the like. Sorbitolmono-oleate is commercially available from Aldrich Chemical Company, ofMilwaukee, Wis., under the trade name “SPAN 80,” while sorbitoltri-oleate is commercially available from Aldrich Chemical Company underthe trade name “SPAN 85.” In certain embodiments of the presentinvention wherein the non-amorphous metallic fibers are coated, thecoating may be present on the non-amorphous metallic fibers in an amountin the range of from about 0.5% to about 5% by weight of the fibers.

In certain embodiments, the high aspect ratio materials present in thecement compositions of the present invention may comprise glass fibers.In certain embodiments, the glass fibers are alkali-resistant (AR) glassfibers, although non-AR glass fibers also may be used in certainembodiments of the present invention. In certain embodiments of thepresent invention where non-AR glass fibers are used, the non-AR glassfibers may be made alkali-resistant through the application of a coatingwith an acrylic acid-based polymer, as will be understood by one ofordinary skill in the art, with the benefit of this disclosure. Incertain embodiments wherein the cement compositions of the presentinvention comprise an alkaline cement, and the high aspect ratiomaterials comprise glass fibers, AR glass fibers may be particularlysuitable. However, when prepared using larger portions of pozzolanic orlatent-hydraulic cement additives (e.g., coal, fly ash, or silica dust),or high aluminate cements, certain embodiments of the cementcompositions of the present invention may have lower pH values, whichmay facilitate the use of non-AR glass fibers. One of ordinary skill inthe art, with the benefit of this disclosure, will recognize the amountsand mixtures of AR and non-AR resistant glass fibers to use depending onthe alkalinity of the cement being used. In certain embodiments, the ARglass fibers may comprise zirconium oxide in an amount in the range offrom about 0.01% to about 15% by weight; in certain other embodiments,the AR glass fibers may comprise zirconium oxide in an amount in therange of from about 10% to about 15% by weight. In certain embodimentsof the present invention, the glass fibers have a length in the range offrom 0.5 to about 13 millimeters, and a diameter in the range of fromabout 10 to about 400 microns. In certain embodiments, the glass fibersmay have an aspect ratio in the range of from about 1.25 to about 5,000.In certain embodiments, the glass fibers may have an aspect ratio in therange of from about 10 to about 1,000, and in certain other embodiments,from about 20 to about 500. Examples of suitable glass fibers include,inter alia, “CEM-FIL® HD” chopped strands and “CEM-FIL® HP” choppedstrands, available from Saint-Gobain Vetrotex America, Inc., of ValleyForge, Pa. Other examples of suitable glass fibers include, inter alia,“E” grade “FIBERGLAST,” available from Fiberglast Development Corp., ofBrookville, Ohio, and “NYCON AR” grade fibers from Nycon, Inc., ofWesterly, R.I. When included in the cement compositions of the presentinvention, the glass fibers may be present in an amount in the range offrom about 0.5% to about 20% bwoc.

In certain embodiments, the high aspect ratio materials present in thecement compositions of the present invention may comprise non-fibrousminerals. Generally, suitable non-fibrous minerals may have a layered,or a platy, structure. The aspect ratio of suitable non-fibrous mineralsmay be determined as a ratio of the length of the non-fibrous mineral toits width. Examples of suitable non-fibrous minerals include, but arenot limited to, micas and vermiculites. In certain embodiments whereinmica is included in the cement compositions of the present invention,suitable micas include, but are not limited to, phlogopites (e.g.,potassium magnesium aluminosilicates), biotites, lepidolites, andmuscovites (e.g., potassium aluminum silicates). Mica materials employedin the present invention may have an aspect ratio in the range of fromabout 50 to about 250. Examples of commercially available mica materialsinclude, but are not limited to, “MICA 5200,” “MICA 5900,” and “MICA6060,” available from Polar Minerals, Inc., in Mt. Vernon, Ind.

Optionally, certain embodiments of the cement compositions of thepresent invention also may include solid materials that may strengthenand reinforce the cement. These solid materials may include both naturaland man-made materials, and may have any shape, including, but notlimited to, beaded, cubic, bar-shaped, flake, fiber, platelets,cylindrical, or mixtures thereof. Suitable such solid materials include,but are not limited to, Wollastonite (CaOSiO₂), basalts, carbon fibers,plastic fibers (e.g., polypropylene and polyacrylic nitrile fibers), andcombinations thereof. In certain embodiments wherein Wollastonite isemployed in the present invention, the Wollastonite may have an aspectratio in the range of from about 11 to about 19 and a mean particle sizein the range of from about 4 to about 40 microns. In certain embodimentswherein basalt is used in the cement composition of the presentinvention, the basalt may have a mean particle size in the range of fromabout 3 mm to about 6 mm, and an aspect ratio in the range of from about130 to about 660. Where included, these additional solid materials maybe added to the cement composition of the present invention individuallyor in combination. Additionally, the solid materials of the presentinvention may be present in the cement composition in a variety oflengths and aspect ratios. One of ordinary skill in the art, with thebenefit of this disclosure, will recognize the mixtures of type, length,and aspect ratio to use to achieve the desired properties of a cementcomposition for a particular application.

Optionally, additional additives may be added to the cement compositionsof the present invention as deemed appropriate by one skilled in the artwith the benefit of this disclosure. Examples of such additives include,inter alia, fly ash, silica compounds, fluid loss control additives,lost circulation materials, a surfactant, a dispersant, an accelerator,a retarder, a salt, a formation conditioning agent, fumed silica,bentonite, microspheres, expanding additives, weighting materials,organic fibers, and the like. For example, the cement compositions ofthe present invention may be foamed cement compositions comprising anexpanding additive that produces gas within the cement composition inorder, inter alia, to reduce the cement composition's density. Anexample of a suitable expanding additive comprises a blend containinggypsum, and is commercially available under the trade name “MICROBOND”from Halliburton Energy Services, Inc., at various locations. One ofordinary skill in the art with the benefit of this disclosure willrecognize the proper amount of an expanding additive to use in order toprovide a foamed cement composition having a desired density. An exampleof a suitable sodium silicate is commercially available from HalliburtonEnergy Services, Inc., under the trade name ECONOLITE®. An example of asuitable additive that demonstrates free-water-reduction andsolids-suspension properties is commercially available from HalliburtonEnergy Services, Inc., of Duncan, Okla., under the trade name “FWCA™.”An example of a suitable dispersant is commercially available fromHalliburton Energy Services, Inc., under the trade name “CFR-3.” Anexample of a suitable fly ash is an ASTM class F fly ash that iscommercially available from Halliburton Energy Services, Inc., under thetrade name “POZMIX® A.” An example of a suitable silica flour iscommercially available from Halliburton Energy Services, Inc., under thetrade name “SSA-1.” An example of a suitable fumed silica is an aqueoussuspension of fumed silica that is commercially available fromHalliburton Energy Services, Inc., under the trade name “MICROBLOCK.” Anexample of a suitable foaming surfactant is commercially available fromHalliburton Energy Services, Inc., under the trade name “ZONESEAL 3000.”An example of a suitable defoamer is commercially available fromHalliburton Energy Services, Inc., under the trade name “D-AIR 3000L.”

An example of a method of the present invention is a method of cementingin a subterranean formation, comprising: providing a cement compositioncomprising water, cement, and non-amorphous metallic fibers having amean aspect ratio in the range of from about 1.25 to about 400;introducing the cement composition into a subterranean formation; andallowing the cement composition to set therein.

Another example of a method of the present invention is a method ofcementing in a subterranean formation, comprising: providing a cementcomposition comprising water, cement, and glass fibers having a meanaspect ratio in the range of from about 1.25 to about 5,000; introducingthe cement composition into a subterranean formation; and allowing thecement composition to set therein.

Another example of a method of the present invention is a method ofcementing in a subterranean formation, comprising: providing a cementcomposition comprising water, cement, and a non-fibrous mineral having amean aspect ratio of at least about 50; introducing the cementcomposition into a subterranean formation; and allowing the cementcomposition to set therein.

To facilitate a better understanding of the present invention, thefollowing examples of preferred embodiments are given. In no way shouldsuch examples be read to limit, or to define, the scope of theinvention.

EXAMPLE 1

Sample cement compositions were prepared by mixing a base cement slurrywith various amounts and grades of chopped steel wool fibers. The basecement slurry comprised Class H cement, 39.42% bwoc water, and 0.25%bwoc FWCA™, and was prepared according to API Recommended Practice 10B,Twenty-Second Edition, December 1997. After the addition of the choppedsteel wool fibers, the samples were stirred at 1,000-2,000 rpm for about2 minutes, then cured at 190° F. for 72 hours at 3000 psi.

Sample Composition No. 1 comprised the base cement slurry, with nofibers.

Sample Composition No. 2 comprised the base cement slurry mixed with 1%GMT-2136 Grade 0 chopped steel wool fibers bwoc.

Sample Composition No. 3 comprised the base cement slurry mixed with 5%GMT-2136 Grade 0 chopped steel wool fibers bwoc.

Sample Composition No. 4 comprised the base cement slurry mixed with 1%GMT-180 Grade 1 chopped steel wool fibers bwoc.

Sample Composition No. 5 comprised the base cement slurry mixed with 3%GMT-180 Grade 1 chopped steel wool fibers bwoc.

Sample Composition No. 6 comprised the base cement slurry mixed with 5%GMT-180 Grade 1 chopped steel wool fibers bwoc.

The compressive and tensile strengths exhibited by the sample cementcompositions are summarized in Table 1, below. The Brazilian TensileStrength Test was performed according to ASTM C496, and useddog-bone-shaped briquettes according to the procedure described for testCRD-C 260-01 in the U.S. Army Corps of Engineers' Handbook for Concreteand Cement. TABLE 1 Density of Density of Density of Brazilian Designtop set middle set bottom set Compressive Tensile Sample Density cementcement cement Strength Strength Composition (lb/gal) (lb/gal) (lb/gal)(lb/gal) (psi) (psi) Sample 16.4 16.4 16.4 16.4 4340 430 Composition No.1 Sample 16.48 16.65 16.7 16.75 3400 500 Composition No. 2 Sample 16.8216.96 17.06 17.09 3800 540 Composition No. 3 Sample 16.48 16.64 16.7216.74 3320 400 Composition No. 4 Sample 16.65 16.87 16.93 16.96 3250 490Composition No. 5 Sample 16.82 16.96 17.06 17.1 3820 460 Composition No.6

Example 1 demonstrates, inter alia, that the cement compositions of thepresent invention comprising fibers having high aspect ratios aresuitable for use in subterranean formations.

EXAMPLE 2

A base cement slurry was prepared according to API Recommended Practice10B, Twenty-Second Edition, December 1997, that comprised Class H cementand 37.34% water-bwoc, and that had a density of 16.74 lb/gal. Sampleswere cured at 190° F. and 3000 psi for 72 hours.

Sample Composition No. 7 comprised the base cement slurry, with no glassfibers.

Sample Composition No. 8 comprised the base cement slurry mixed with0.75% CEM-FIL® HD AR bwoc using API mixing procedures.

Sample Composition No. 9 comprised the base cement slurry mixed by handwith 0.75% CEM-FIL® HD bwoc.

Sample Composition No. 10 comprised the base cement slurry mixed by handwith 1.5% CEM-FIL® HD bwoc.

Sample Composition No. 11 comprised the base cement slurry mixed with0.75% FiberGlast 29 bwoc using API mixing procedures.

Sample Composition No. 12 comprised the base cement slurry mixed with1.5% FiberGlast 29 bwoc using API mixing procedures.

Sample Composition No. 13 comprised the base cement slurry mixed with0.75% FiberGlast 38 bwoc using API mixing procedures.

The compressive and tensile strengths exhibited by the samplecompositions are summarized in Table 2, below. TABLE 2 CompressiveTensile Sample Composition Strength (psi) Strength (psi) SampleComposition No. 7 5380 522 Sample Composition No. 8 4746 470 SampleComposition No. 9 4642 560 Sample Composition No. 10 6060 650 SampleComposition No. 11 6042 712 Sample Composition No. 12 6445 642 SampleComposition No. 13 6190 660

Example 2 demonstrates, inter alia, that the sample compositionscomprising glass fibers exhibited compressive and tensile strengthscomparable to, or significantly better than those exhibited by the basecement slurry. Furthermore, both AR and non-AR glass fibers hadbeneficial effects on the strength of the sample cement compositions.

EXAMPLE 3

Sample cement compositions were prepared according to the followingprocedure: Class G cement and silica flour (SSA-1) were added to amixture of seawater and calcium chloride solution according to APIRecommended Practice 10B, Twenty-Second Edition, December 1997. Thecomposition then was transferred to a foam blender, and the foamingsurfactant ZONESEAL 3000 was added, in varying amounts. The compositionwas stirred at high speed for 15-30 seconds, while foaming wascompleted. For certain compositions comprising glass fibers, the glassfibers were hand mixed into the composition with a spatula. Tensilestrengths of the cured cement compositions were measured according toCRD-C 260-01.

Sample Composition No. 14 comprised Class G cement, 49.45% seawaterbwoc, 35% SSA-1 bwoc, 2.5% ZONESEAL 3000 by weight of the water, 0.49gal/sack 33% CaCl₂ solution, and no glass fibers.

Sample Composition No. 15 comprised Class G cement, 49.45% seawaterbwoc, 35% bwoc SSA-1, 2.5% ZONESEAL 3000 by weight of the water, 0.49gallons/sack 33% CaCl₂ solution, and 14.35% CEM-FIL® HP glass fibers byvolume of the foamed slurry.

Sample Composition No. 16 comprised Class G cement, 49.45% seawaterbwoc, 35% bwoc SSA-1, 2.5% ZONESEAL 3000 by weight of the water, 0.49gallons/sack 33% CaCl₂ solution, and 28.67% CEM-FIL® HP glass fibers byvolume of the foamed slurry.

Sample Composition No. 17 comprised Class G cement, 49.45% seawaterbwoc, 35% SSA-1 bwoc, 1.5% ZONESEAL 3000 by weight of the water, 0.65gallons/sack 33% CaCl₂ solution, and 14.35% CEM-FIL® HP glass fibers byvolume of the foamed slurry.

Sample Composition No. 18 comprised Class G cement, 129.66% seawaterbwoc, 22.5% SSA-1 bwoc, 2.02 gallons/sack MICROBLOCK, 0.23 gallons/sackECONOLITE®, and no glass fibers.

Sample Composition No. 19 comprised Class G cement, 129.66% seawaterbwoc, 22.5% SSA-1 bwoc, 2.02 gallons/sack MICROBLOCK, 0.23 gallons/sackECONOLITE, and 30% CEM-FIL® HP glass fibers by volume of the cementslurry.

Sample Composition No. 20 comprised Class G cement, 129.66% seawaterbwoc, 22.5% SSA-1 bwoc, 2.02 gallons/sack MICROBLOCK, 0.46 gallons/sackECONOLITE, and 30% CEM-FIL® HP glass fibers by volume of the cementslurry.

The sample compositions were cured under a variety of curing conditions,set forth below.

Curing Condition A consisted of curing at room temperature for 2-3 days,followed by curing at 60° C. in a water bath for 3 days.

Curing Condition B consisted of curing at room temperature for 2-3 days,followed by curing at 160° C. and 3000 psi for 3 days.

Curing Condition C consisted of curing at room temperature for 2-3 days,followed by curing at 130° C. and 3000 psi for 3 days.

Curing Condition D consisted of curing at room temperature for 2-3 days,followed by curing at 120° C. and 3000 psi for 3 days.

Curing Condition E consisted of curing at room temperature for 2-3 days,followed by curing at 110° C. and 3000 psi for 3 days.

The tensile strengths exhibited by the sample compositions after curingunder the various curing conditions are summarized in Table 3, below.TABLE 3 Unfoamed Foamed Curing Slurry Density Slurry Density TensileSample Composition Conditions (lb/gal) (lb/gal) Strength (psi) SampleComposition A 16.3 13.0 160 No. 14 Sample Composition B 16.3 13.0 427No. 14 Sample Composition A 16.3 13.0 364 No. 15 Sample Composition B16.3 13.0 326 No. 15 Sample Composition A 16.3 13.8 306 No. 16 SampleComposition C 16.3 13.8 398 No. 16 Sample Composition A 14.8 12.5 220No. 17 Sample Composition B 14.8 12.5 219 No. 17 Sample Composition A12.5 N.A. 112 No. 18 Sample Composition B 12.5 N.A. 81 No. 18 SampleComposition A 12.5 N.A. 191 No. 19 Sample Composition C 12.5 N.A. 169No. 19 Sample Composition C 12.5 N.A. 138 No. 20 Sample Composition D12.5 N.A. 220 No. 20 Sample Composition E 12.5 N.A. 245 No. 20

As shown in Table 3, the inclusion of AR glass fibers improved thetensile strengths of both foamed and unfoamed cement compositions.

EXAMPLE 4

Impact strength tests were performed on sample cement compositions thatcomprised Class H cement, 39.4% water bwoc, and 0.25% FWCA™ bwoc. Fiberswere added to certain cement compositions, between 500-2000 rpm, afterthe cement compositions had been prepared according to API RecommendedPractice 10B, Twenty-Second Edition, December 1997. For certaincompositions, the fibers were coated with a surfactant (sorbitolmono-oleate mixed with isopropyl alcohol (“IPA”) in a 1:1 weight ratio).The IPA-sorbitol mono-oleate mixture then was applied to certain of thefibers in an amount sufficient to coat the fibers with a net weight of0.5%, 1.5%, or 3.0% of sorbitol mono-oleate. The coated fibers wereagitated by tumbling overnight, and the IPA was allowed to evaporate ina lab hood. The sample cement compositions were cured either in a waterbath at 190° for 72 hours (“Method A”) or in an autoclave at 190° F. for72 hours under 3000 psi (“Method B”). Compressive strengths weremeasured according to API Recommended Practice 10B. Tensile strengthswere measured according to CRD-C 260-01.

Impact strength tests were performed with a Gardner Impact Tester, Model#5510, manufactured by Paul N. Gardner Co. Inc., ofLauderdale-by-the-sea, Florida. The dropping weight comprised a 2 poundmetal cylinder having a ball diameter of 0.5%. A procedure was developedthat provided for differentiation of sample compositions havingdifferent impact strengths. First, the sample cement compositions werepoured with 2″×2″×2″ brass molds, and cured by either Method A or MethodB above. Once removed from the mold, the cured sample cementcompositions were submerged in water until testing.

The smooth side of the cured sample cement composition was placed on thedye plate of the impact tester. While the cured cement composition washeld in place, the dropping weight was raised to a height of about 15inches in the guide tube, then allowed to fall freely. If the curedsample cement composition did not split into separate pieces, thedropping weight was raised again and allowed to drop on the scope impactspot as before. If the cured sample cement composition remained unbrokenafter 9 impacts, the height from which the dropping weight was to bedropped was increased to 20 inches. The process was repeated, and if thecured sample cement composition survived 9 impacts from 20 inches, thedrop height then was increased to 30 inches, and the process agent wasrepeated.

The results of the testing are set forth in the table below. TABLE 4Steel Impacts Impacts Impacts Compressive Tensile Sample Wool FiberSurfactant Slurry Curing From From From Strength Strength CompositionFibers Concentration Concentration Density Method 15″ 20″ 30″ (psi)(psi) Sample None None None 16.4 B 1 0 0 4340 430 Composition No. 21Sample GMT- 3% None 16.65 A 5.5 0 0 3050 400 Composition 2136 bwoc No.22 Sample GMT- 3% None 16.65 A 5 0 0 3190 370 Composition 180 bwoc No.23 Sample GMT- 3% None 16.65 A 5 0 0 3010 410 Composition 380 bwoc No.24 Sample GMT- 3% None 16.65 B 9 5 0 3670 N.D. Composition 180 bwoc No.25 Sample GMT- 3% 0.5% by 16.65 B 9 9 1 4020 N.D. Composition 180 bwocweight of No. 26 fiber Sample GMT- 3% 1.5% by 16.65 B 9 9 3 3880 N.D.Composition 180 bwoc weight of No. 27 fiber Sample GMT- 3% 3% by 16.65 BOne drop from a height of 3430 N.D. Composition 180 bwoc weight of 40inches No. 28 fiber

In Table 4, “N.D.” indicates that the tensile strength of a particularsample composition was not determined.

Example 4 demonstrates, inter alia, that cement compositions of thepresent invention comprising steel wool fibers possess desirable impactstrengths, and that the application of a coating to the steel woolfibers may further increase the impact strength of a cement composition.

EXAMPLE 5

A variety of sample cement compositions were prepared as follows.

Sample Composition No. 29 was prepared according to API RecommendedPractice 10B, Twenty-Second Edition, December 1997, by mixing 56% ClassH cement bwoc, 22% POZMIX® A bwoc, 22% fumed silica bwoc, and 2% bwocbentonite. This mixture then was added to 112.6% bwoc water and 0.125gallons of D-AIR 300L per sack of Class H cement.

Sample Composition No. 30 was prepared similarly to Sample CompositionNo. 29, except that 1% carbon fibers were added to the solid mixture ofcement, POZMIX® A, fumed silica, and bentonite. The carbon fibers weresupplied by Halliburton Energy Services, Inc., under the trade name “FDPC684-03.” After the addition of the carbon fibers to the solid mixture,and after the addition of water and D-AIR 3000L, 1% CEM-FIL HD AR gradeglass fibers bwoc were hand mixed into the composition.

Sample Composition No. 31 was prepared similarly to Sample CompositionNo. 30, except that the CEM-FIL HD AR grade glass fibers were added inthe cement of 2% bwoc.

Sample Composition No. 32 were prepared similarly to Sample CompositionNo. 31, except that the CEM-FIL HD AR grade glass fibers were added inthe cement of 4% bwoc.

The compressive strength and tensile strengths of the cementcompositions were measured according to the procedures describedearlier, and are set forth in the table below. TABLE 5 CompressiveTensile Sample Composition Strength (psi) Strength (psi) SampleComposition No. 29 1210 90 Sample Composition No. 30 1470 260 SampleComposition No. 31 1570 170 Sample Composition No. 32 1300 175

Example 5 demonstrates, inter alia, that the cement compositions of thepresent invention comprising a mixture of carbon fibers and glass fiberspossess desirable compression strengths and tensile strengths.

EXAMPLE 6

Sample cement compositions were prepared comprising Class H cement, 15%fumed silica bwoc, 25% POZMIX® A bwoc, 1% CFR-3 bwoc, and 0.05 gallonsD-AIR 3 per sack of Class H cement. The sample cement compositionsfurther comprised glass spheres commercially available from 3MCorporation of St. Paul, Minn., under the trade name SCOTCHLITE K46, indiffering amounts. Mica was added to some of the sample compositions.The sample composition further comprised different amounts of water.

The curing conditions of each sample composition, along with certainmechanical properties, are set forth in the table below. Whereperformed, the compressive strength and tensile strength of the cementcompositions were carried out according to the testing procedurespreviously described. TABLE 6 Particle % Beads Water Tensile Comp.Sample Mica Size, Aspect Mica % % Density Curing Strength, Str.Composition Name microns Ratio bwoc bwoc bwoc ppg Conditions psi psiSample None N.A. N.A. N.A. 22 55.6 12 100° F., 130 N.D. Composition 72hrs, No. 33 3000 psi Sample 5900 70 50 10 25 53 12 100° F., 251 N.D.Composition 72 hrs, No. 34 3000 psi Sample None N.A. N.A. N.A. 25 57.711.6 195° F., 457 5480 Composition 72 hrs, No. 35 3000 psi Sample 6060250 60 3 25.7 57.7 11.6 195° F., 540 5040 Composition 72 hrs, No. 363000 psi Sample None N.A. N.A. N.A. 25 57.7 11.6 150° F., 224 5258Composition 48 hrs, atm. No. 37 pressure Sample 6060 250 60 3 25.7 57.711.6 150° F., 293 4713 Composition 48 hrs, atm. No. 38 pressure

In Table 6, “N.D.” indicates that the tensile strength of a particularsample composition was not determined, and “N.A.” indicates that aparticular measurement was not applicable.

The above example demonstrates, inter alia, that the cement compositionsof the present invention comprising mica may be suitable for use insubterranean formations.

Therefore, the present invention is well adapted to carry out theobjects and attain the ends and advantages mentioned as well as thosewhich are inherent therein. While the invention has been depicted anddescribed by reference to certain embodiments of the invention, such areference does not imply a limitation on the invention, and no suchlimitation is to be inferred. The invention is capable of considerablemodification, alternation, and equivalents in form and function, as willoccur to those ordinarily skilled in the pertinent arts and having thebenefit of this disclosure. The depicted and described embodiments ofthe invention are only, and are not exhaustive of the scope of theinvention. Consequently, the invention is intended to be limited only bythe spirit and scope of the appended claims, giving full cognizance toequivalents in all respects.

1. A method of cementing in a subterranean formation, comprising:providing a cement composition comprising water, cement, and a highaspect ratio material selected from glass fibers and non-fibrousminerals; introducing the cement composition into a subterraneanformation; and allowing the cement composition to set therein.
 2. Amethod of cementing in a subterranean formation, comprising: providing acement composition comprising water, cement, and glass fibers having amean aspect ratio in the range of from about 1.25 to about 5,000;introducing the cement composition into a subterranean formation; andallowing the cement composition to set therein.
 3. The method of claim2, wherein the cement is a hydraulic cement.
 4. The method of claim 2,wherein the cement is a calcium phosphate cement or a calcium aluminatecement.
 5. The method of claim 2, wherein the water is present in anamount in the range of from about 30% to about 180% by weight of thecement.
 6. The method of claim 2, wherein the water is present in anamount in the range of from about 40% to about 50% by weight of thecement.
 7. The method of claim 2, wherein the glass fibers arealkali-resistant glass fibers that comprise zirconium oxide.
 8. Themethod of claim 7, wherein the zirconium oxide is present in thealkali-resistant glass fibers in an amount in the range of from about0.01% to about 15% by weight.
 9. The method of claim 2, wherein theglass fibers are present in an amount in the range of from about 0.5% toabout 20% by weight of the cement.
 10. The method of claim 2, whereinthe glass fibers have a mean length in the range of from about 0.5millimeters to about 13 millimeters.
 11. The method of claim 2, whereinthe glass fibers have a diameter in the range of from about 10 to about400 microns.
 12. The method of claim 2, wherein the glass fibers havebeen coated with an acrylic acid-based polymer.
 13. The method of claim2, wherein the glass fibers have a mean aspect ratio in the range offrom about 10 to about 1,000.
 14. A method of cementing in asubterranean formation, comprising: providing a cement compositioncomprising water, cement, and a non-fibrous mineral having a mean aspectratio of at least about 50; introducing the cement composition into asubterranean formation; and allowing the cement composition to settherein.
 15. The method of claim 14, wherein the cement is a calciumphosphate cement or a calcium aluminate cement.
 16. The method of claim14, wherein the water is present in an amount in the range of from about30% to about 180% by weight of the cement.
 17. The method of claim 14,wherein the non-fibrous mineral has a layered structure.
 18. The methodof claim 14, wherein the non-fibrous mineral has a platy structure. 19.The method of claim 14, wherein the non-fibrous mineral comprises mica,vermiculite, or a mixture thereof.
 20. The method of claim 14, whereinthe non-fibrous mineral is mica that has a mean aspect ratio in therange of from about 50 to about 250.